JP2005168119A - Spindle motor and recording disk drive equipped therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spindle motor with the noise and vibration reduced. <P>SOLUTION: The spindle motor is mounted in a recording disk drive and turns recording disks. A bush, substantially in cylindrical shape, is fit into the inner circumferential surface of a hole formed in a base plate that constitutes part of the enclosure of the recording disk drive and forms the base of the spindle motor. A dynamic pressure bearing unit that rotatably supports a rotating body by the dynamic pressure of fluid during rotation is fit into the inner circumference of the bush. A stator is fit onto the outer circumferential surface of the bush. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a spindle motor that rotates a recording disk, and a recording disk drive apparatus that includes the spindle motor.

  A hard disk drive, which is a typical recording disk drive, has a smaller disk diameter as the storage capacity per unit area of the hard disk, which is the recording medium, increases. As a result, hard disk drives are used in personal computers as usual, as well as home appliances such as digital video / DVD (Digital Versatile Disk) decks, home game consoles, and car navigation systems. It is also used for in-vehicle devices. In addition, use for portable devices such as digital video cameras and PDAs (Personal Digital Assistance) is also being considered.

  In particular, in the case of a hard disk drive mounted on an audio / video device or a portable device, the noise generated by the hard disk drive is more unpleasant to the user than a hard disk drive used for other purposes. For this reason, a dynamic pressure bearing using dynamic pressure of a fluid such as lubricating oil or gas is used as a bearing of a spindle motor mounted on a hard disk drive, instead of a ball bearing having a large sliding sound.

In order to achieve miniaturization and thinning of the hard disk drive and to reduce its cost, a base plate formed with a part of the hard disk drive housing and a bracket forming the base of the spindle motor as one member is used. ing. (Patent Document 1)
However, as the entire hard disk drive becomes smaller and thinner, the base plate has its natural frequency at a high frequency range that makes humans feel uncomfortable. On the other hand, the number of revolutions of the spindle motor increases as the ability of the recording disk drive device to read and write information increases. For this reason, resonance with the natural frequency of the base plate occurs particularly in a frequency band close to the natural frequency of the base plate, and noise in a high frequency range uncomfortable for human hearing is generated. This noise was not a big problem when a ball bearing with a large bearing sliding noise was used. However, when a dynamic pressure bearing was used, the noise generated by the bearing was small and particularly noticeable.

JP 2003-153491 A

(1) Vibration and noise of the base plate The housing of the recording disk drive device is located on the outermost side among the components of the device, and the vibration is easily transmitted to the outside air. For this reason, when the housing of the recording disk drive device vibrates, the noise is more likely to be heard outside than the sound produced by the vibration of other members constituting the recording disk drive device. In addition, human hearing is particularly sensitive to high-frequency sounds, and sounds from 1000 Hz to 7000 Hz tend to be heard louder than other sound ranges.

  The factors that cause the base plate that forms a part of the housing of the recording disk drive device and forms the base of the spindle motor that rotates the recording disk can be roughly divided into the following three.

  The first is vibration caused by rotational motion, which is caused by non-uniform rotation when the spindle motor and recording disk rotate. However, such vibration is not a cause of high-frequency noise that is particularly uncomfortable at a standard recording disk speed (3600 to 12,000 revolutions per minute = 60 to 200 Hz). In addition, as machining accuracy is improved, vibration due to non-uniform rotation has been greatly reduced in recent years.

  Secondly, vibrations caused by electromagnetic force are transmitted to the base through the rotating member.

  In general, a spindle motor mounted on a recording disk drive device is an induction generated by alternately reversing a coil with a constant period by flowing a current in the forward and reverse directions through the stator coil according to a constant period. The rotating member rotates by the magnetic field acting alternately by the magnetic field formed by the rotor magnet fixed to the rotating member, and the attractive force and the repulsive force. However, the attractive or repulsive force of the magnetic field does not act only because the rotating member rotates. The forces acting in directions other than the rotation direction generate vibrations having a certain period, and such vibrations are called electromagnetic vibrations. The vibration includes components with different frequencies over a wide frequency band, and this vibration component can be easily obtained by Fourier-expanding the experimentally obtained vibration wave and calculating the amplitude coefficient of the expansion. it can.

  The rotor magnet is one of the places where electromagnetic vibration is generated, and the vibration is transmitted to the hydrodynamic bearing portion through the rotating member. During high-speed rotation, the dynamic pressure of the dynamic pressure bearing is high, and the vibration attenuation at the dynamic pressure bearing is small. When the dynamic pressure bearing portion is directly fixed to the base plate as in the prior art, resonance occurs in the vicinity of the natural frequency of the base plate among the vibration components of the electromagnetic vibration transmitted through the dynamic pressure bearing portion.

  The natural frequency of the base plate depends on the specific elastic modulus, thickness, shape, and the like of the member. If the same material is used, the natural frequency becomes higher as the base plate becomes thinner.

  The third factor is caused by the electromagnetic force as in the second factor, but the stator vibrates to excite the vibration of the base.

  The magnetic force acting between the rotor magnet and the stator vibrates the rotor magnet and at the same time vibrates the stator as a reaction. When the stator is a general three-phase, nine-pole, and rotated by a method called 120-degree energization, the switch is switched six times per rotation of the motor. The rotational speed of the recording disk is generally about 3600 revolutions per minute to 12,000 revolutions per minute, and the switching frequency is about 360 Hz to 1200 Hz. From past experiments, it is known that the amplitude of the 15th to 25th order in the Fourier expansion of the vibration of the stator is large, and it is a high-range sound that human hearing senses at just 5500-30000 Hz. Conventionally, the stator is attached to a base plate that constitutes a part of the casing of the recording disk drive device. The vibration of the stator directly vibrates the base plate, and resonance occurs in the vicinity of the natural frequency of the base plate.

  There are roughly two methods for removing the second and third causes. One is a method of preventing resonance by lowering the natural frequency of the base plate or by making the natural frequency of the base plate not match the frequency of electromagnetic vibration generated by the stator and the rotor magnet. The other is a method of damping between the stator and the base plate so that electromagnetic vibration is not transmitted to the base plate.

  However, since the base plate is usually manufactured by die casting or press molding, and changing its mold requires a large amount of money, it is not easy to change the natural frequency by changing the shape of the base plate.

(2) Diversification of models As described in the prior art, in recent years, the use of recording disk drive devices has expanded, and there are various specifications according to the use. In particular, if the number of recording disks to be mounted and the number of rotations thereof are different, it is very difficult to optimize the design in order to satisfy the specifications of the same model. Therefore, another model is prepared according to the specifications of the recording disk drive device, and it is necessary to redesign the spindle motor production equipment such as the dynamic pressure bearing unit, the entire spindle motor including the base plate, and the jig.

  Usually, die casting or press working is used for the base plate of the disk drive device, and changing the mold according to the change of the shape of the base plate requires a great deal of cost. In addition, manufacturing jigs are expensive because they require high processing accuracy and durability, and increasing their types requires individual maintenance.

(3) Problem to be Solved by the Present Invention Accordingly, the problem to be solved by the present invention is that a substrate of a spindle motor that constitutes a part of a casing of a recording disk drive and is mounted on the recording disk drive. Reducing vibration and noise caused by electromagnetic force of the base plate
It is to reduce the cost and development cost of reworking expensive production equipment jigs and molds as the spindle motor specifications and models are changed, thereby improving productivity and shortening development time.

The spindle motor according to claim 1,
A spindle motor that is mounted on a recording disk drive device and rotates the recording disk, and generates a magnetic field when an electric current is passed, and a base plate that forms part of the casing of the recording disk device and forms the base of the spindle motor A substantially cylindrical bush fixed between the stator and the base plate, a dynamic pressure bearing unit fixed to the bush, a rotating member supported rotatably with respect to the base plate via the dynamic pressure bearing unit, And a rotor magnet fixed to the rotating member so as to face the stator.

The spindle motor according to claim 2,
The base plate described in claim 1 is provided with a circular hole, and a part of the outer peripheral surface of the bush is fitted and fixed to the hole.

The spindle motor according to claim 3 is
The hydrodynamic bearing unit according to claim 1 includes a rotating shaft provided at a rotation center portion of the rotating member and a cylindrical sleeve that rotatably supports the rotating shaft, and an outer peripheral surface of the rotating shaft and an inner portion of the sleeve. A radial dynamic pressure bearing portion that supports a load in the radial direction is provided between the peripheral surface and the peripheral surface.

Furthermore, the spindle motor according to claim 4,
A material having vibration damping properties is used as a material for forming the bush according to any one of claims 1 to 3.

The spindle motor according to claim 5 is
A high-strength material is used as a material for forming the bush according to any one of claims 1 to 3.

The recording disk drive device according to claim 6,
A spindle motor according to any one of claims 1 to 5;
A recording disc on which information is recorded;
Information access means for reading information from the recording disk and / or writing information to the recording disk.

  In the spindle motor according to claim 1, a bush is interposed between the base plate, which is the substrate, and the hydrodynamic bearing unit. As a result, there are at least two joint portions between the bearing unit and the base plate. In general, the amplitude of the vibration tends to attenuate as the wavelength becomes shorter (the frequency becomes higher). The higher the frequency, the higher the vibration energy, but a slight friction occurs at the joint between the members, and the vibration causes a loss in vibration energy, so that the vibration amplitude is greatly attenuated. Further, this bush is fitted with a stator. When the fastening strength between the stator and the bush is sufficiently high, not only the stator vibrates, but the bush and the stator are vibrated together, and the electromagnetic vibration mode of the stator is changed to the material of the bush. Depending on the shape or the like, it can be shifted to a high sound range or a low sound range.

  In this way, resonance with high frequency components of electromagnetic vibration caused by electromagnetic force does not occur, and vibration and noise are reduced.

  Further, according to this structure, the dynamic pressure bearing portion is unitized to form a dynamic pressure bearing unit, and the dynamic pressure bearing unit and the base plate are attached via the bush. As a result, a hydrodynamic bearing unit of a different specification or model can be placed on the base plate simply by changing the shape of the hydrodynamic bearing unit mounting portion of the bush. That is, if the base plate and jig are made in advance according to the outer shape of the bush, it is not necessary to change the shape of the base plate and jig. Therefore, it is possible to reduce the cost for the production equipment and the time and cost for developing the base plate and the jig. Moreover, the troublesome maintenance of the jig according to the model type is eliminated, and the productivity can be improved.

  The spindle motor according to claim 2 is provided with a hole for fitting the bush into the base plate, so that the mounting of the bush on the base plate is facilitated, and the workability during production is improved.

  A spindle motor according to a third aspect of the present invention is the dynamic pressure bearing unit according to the first aspect, wherein the dynamic pressure bearing unit is formed from a rotating shaft fixed to the rotation center of the sleeve and the rotating member, and is a radial dynamic pressure bearing. Is formed. Generation of noise can be reduced by using the hydrodynamic bearing, and the motor can be stabilized by securing the radial bearing so that the bearing rigidity is not lowered even if the bearing is downsized.

  In the spindle motor according to the fourth aspect, the bush is made of a material having vibration damping properties. A material having damping properties has a large energy loss inside the member with respect to vibration, and therefore vibrations in the high frequency range are particularly damped. In other words, the bush formed of a material having damping properties serves as a filter for vibration components corresponding to the high sound range. Therefore, among the components of the electromagnetic vibration generated in the rotor magnet and the stator, a high frequency component close to the natural frequency of the base plate is attenuated in the bush, and noise can be reduced.

  In the spindle motor according to the fifth aspect, the bush is formed of a high-strength member. Therefore, even if the fastening strength with the stator is increased, the non-uniform deformation of the bush is small. By firmly fixing the stator and the bush, the stator and the bush are vibrated together, and the frequency at which the frequency component of electromagnetic vibration peaks can be changed. Therefore, among the components of the electromagnetic vibration generated in the stator in particular, the frequency of the high frequency component close to the natural frequency of the base plate is shifted, and noise can be reduced.

  Since the recording disk drive apparatus according to the sixth aspect is equipped with the spindle motor having the structure according to any one of the first to fifth aspects of the present invention, the base plate constituting a part of the casing of the recording disk drive apparatus vibrates. By not doing so, noise due to electromagnetic vibration can be reduced as a whole apparatus. In addition, errors that occur when reading and writing information can be reduced by reducing vibration.

  Embodiments of a spindle motor and a recording disk device including the spindle motor according to the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a spindle motor 2 mounted on the recording disk drive device 1. FIG. 2 is a cross-sectional view of the recording disk drive device 1 of the present invention equipped with a spindle motor 2 having the configuration of the present invention.

(1-1) Configuration of Recording Disk Drive Device A base plate 3 that forms the base of the spindle motor 2 constitutes a part of the housing of the recording disk drive device 1, and the spindle of the recording disk drive device 1 has a spindle. A motor 2 and a disk-shaped recording disk D, a head H that reads and writes information on the recording disk D, an arm A that supports the head H, and an actuator P that moves the head H are provided.

(1-2) Configuration of Spindle Motor The spindle motor 2 shown in FIG. 1 includes a rotor hub 4 that is a rotating member, a dynamic pressure bearing unit 8, a bush 5, a base plate 3, a stator 6, and a rotor magnet 7. Has been.

(1-3) Fixing of recording disk to spindle motor The rotor hub 4 which is a rotating member has a rotor hub collar 14 on the outer peripheral surface, and the recording disk D is placed on the rotor hub collar 14. . When a plurality of recording disks D are mounted, a spacer S is provided between the recording disks D, and a certain distance is maintained between the recording disks D. In order to prevent the recording disk D from flying off, the uppermost recording disk D is pressed against the rotor hub 4 by the clamper C, and the clamper C is attached to the rotor hub 4 with screws B.

(1-4) Rotor hub that is a rotating member of a spindle motor and retainer The rotor hub 4 that is a rotating member is integrally provided with a rotating shaft 9 at the center of rotation, and the rotating shaft 9 is attached to a cylindrical sleeve 10. It is inserted. A cylindrical bearing housing 11 with a bottom is provided around the sleeve 10. The rotor hub 4 is provided with a cylindrical peripheral wall portion 24 so as to surround the outer periphery in the vicinity of the opening end of the sleeve 10 and the bearing housing 11, and the stopper 12 is fixed to the open end portion of the cylindrical peripheral wall portion 24. Due to the retainer 12, the relative movement in the axial direction between the rotor hub 4 and the bearing housing 11 is restricted.

(1-5) Hydrodynamic bearing unit of spindle motor A herringbone-shaped shallow groove (not shown) is formed on one or both of the outer peripheral surface of the rotary shaft 9 and the inner peripheral surface of the sleeve 10. Lubricating fluid is held in a radial gap between the outer peripheral surface of the rotating shaft 9 and the inner peripheral surface of the sleeve 10. Thus, a radial dynamic pressure bearing 8a is formed that increases the pressure of the lubricating fluid and generates a load support pressure during the relative rotation of the rotating shaft 9 and the sleeve 10. Further, a part of the shaft-side flat surface of the rotor hub 4 is opposed to the flat surface provided at the opening end of the bearing housing 11. Spiral shallow grooves (not shown) are formed on one or both of these flat surfaces, and a lubricating fluid is held in the axial gap between the flat surfaces. Thus, a thrust dynamic pressure bearing 8b is formed that generates a load supporting pressure in the axial direction when the rotor hub 4 and the bearing housing 11 are rotated relative to each other. The lubricating fluid is continuously held in the radial dynamic pressure bearing 8 a, the thrust dynamic pressure bearing 8 b, the gap between the sleeve 10 and the rotating shaft 9. A cylindrical peripheral wall portion is provided on the shaft-side flat surface of the rotor hub 4 so as to surround the outer periphery of the bearing housing 11. A cylindrical peripheral wall portion 24 and the outer peripheral surface of the upper end portion of the bearing housing 11 opposed to the cylindrical peripheral wall portion 24 form a tapered portion 8 c in which the gap widens toward the opening end of the cylindrical peripheral wall portion 24. The taper portion 8c is provided with a unique interface 8d between the lubricating fluid and the outside air.

  The dynamic pressure bearing unit 8 includes a radial dynamic pressure bearing 8 a that rotatably supports the rotor hub 4 that is a rotating member, a member that constitutes the thrust dynamic pressure bearing 8 b, and a part of the rotor hub 4. In the present invention, it goes without saying that a hydrodynamic bearing unit having a configuration different from that described in the present embodiment can be used.

(1-6) Base Plate The base plate 3 constituting a part of the housing of the recording disk drive device 1 is a plate-like aluminum alloy and is formed by press working. Aluminum and its alloys are suitable for press working, and the productivity is improved by forming by pressing, and it is possible to form into a complicated shape required for the casing of the recording disk drive device 1, Furthermore, it has the precision required for the substrate of the spindle motor 2.

  Depending on the application of the base plate, plate-like stainless steel may be formed by press working in order to increase the strength of the entire apparatus. Further, it may be formed by processing other than press processing such as die casting according to required specifications and characteristics.

  The base plate 3 has a hole 13 for fitting the bush 5 therein. Further, the hole 13 is formed with a diameter-enlarged hole diameter portion 23 on the outer peripheral surface of the upper end portion of the hole 13 in order to accurately match the axial position of the bush 5 in accordance with the shape of the outer peripheral surface of the bush 5. Yes. Accordingly, the shape of the base plate 3 can be made common only by manufacturing a bush corresponding to the shape of the hole 13 of the base plate 3 and corresponding to the plurality of recording disk drive models and the plurality of hydrodynamic bearing units. Is done.

(1-7) Stator and Rotor Magnet of Spindle Motor The stator 6 includes a 9-slot stator core and a three-phase coil wound around each tooth of the stator core. A sensorless system is used in which the two-phase coils are energized, the induced electromotive force generated in the remaining one-layer coil is converted into a digital signal, and the coil current of each phase is switched. The rotor hub 4 of the spindle motor 2 is rotated by a rotational force due to electromagnetic interaction between the rotor magnet 7 fixed to the rotor hub 4 and the stator 6 whose coil current is controlled opposite to the rotor magnet 7.

(1-8) Spindle Motor Bush A substantially cylindrical bush 5 is interposed between the base plate 3 and the hydrodynamic bearing unit 8. The bush 5 includes a small-diameter short cylindrical portion 5a constituting the lower portion and a thick and large-diameter thick portion 5b constituting the upper portion. The short cylindrical portion 5 a is fitted in the hole 13 of the base plate 3, and a part of the thick wall portion 5 b is fitted in a hole expanding portion 23 provided in the hole 13 of the base plate 3. A bearing housing 11 that constitutes the hydrodynamic bearing unit 8 is fitted into the bush, and a stator 6 is fitted over the thick portion 5 b of the bush 5.

  If the area of the contact surface between the bush 5 and the base plate 3 and / or the contact surface between the bush 5 and the hydrodynamic bearing unit 8 is reduced, vibrations may not be transmitted.

  The bush 5 is made of stainless steel, which is a high strength member. If the bush 5 is made of stainless steel, even if the stator 6 formed of a silicon steel plate is firmly fastened, non-uniform distortion is unlikely to occur, so the mode of vibration of the stator 6 can be shifted. ing.

  In addition, since the member which forms the bush 5 should just have a certain level or more mechanical strength, you may use aluminum, its alloy, brass, etc. in addition. In order to facilitate the cutting process, it is more preferable to use a metal having free cutting ability.

  Further, laser welding is used to secure the fastening strength of the bush 5 to the base plate 3.

  An adhesive may be used for fixing the bush 5 and the base plate 3 instead of laser welding. When an adhesive is used, the fastening strength is reduced, but the adhesive can act as an elastic agent to moderate vibrations.

  The spindle motor 102 shown in FIG. 3 is an embodiment using another dynamic pressure bearing unit 108 while using the same base plate 103 as in the first embodiment.

(2-1) Configuration of Recording Disk Drive Device A part of the housing of the recording disk drive device 101 (not shown) is composed of a base plate 103 that forms the base of the spindle motor 102 shown in FIG. The recording disk 101 (not shown) includes a recording disk D, a head H (not shown) that reads and writes information on the recording disk D, an arm A (not shown) that supports the head H (not shown), And an actuator P (not shown) for moving the arm A (not shown).

(2-2) Configuration of Spindle Motor As in the first embodiment, the spindle motor 102 shown in FIG. 3 includes a rotor hub 104 that is a rotating member, a dynamic pressure bearing unit 108, a bush 105, a base plate 103, and a stator. 106 and a rotor magnet 107. Compared with the spindle motor 2 described in the first embodiment, the spindle motor 102 has one recording disk D fixed to the rotor hub 104, and the rotor hub 104, the stator 106, the rotor magnet 107, the bearing unit 108, and the bush. Although the shape of the inner peripheral surface 105 is changed in accordance with the change in the number of recording disks D, the base plate 103 constituting a part of the casing of the recording disk drive 101 (not shown) is provided. The substrate of the spindle motor 102 is formed and has the same shape as the base plate 3 constituting a part of the housing of the recording disk drive device 1 in the first embodiment.

(2-3) Fixing of Recording Disk to Spindle Motor The rotor hub 104, which is a rotating member, has a rotor hub collar 114 on its outer peripheral surface, and the recording disk D is placed on the rotor hub 114. In order to prevent the recording disk D from flying off, the recording disk D is pressed against the flange 114 of the rotor hub 104 by the clamper C, and the clamper C is attached to the rotor hub 104 by screws B.

(2-4) Rotor hub that is a rotating member of a spindle motor and retainer The rotor hub 104 that is a rotating member has a rotating shaft 109 fixed at the center of rotation, and the rotating shaft 109 is inserted through a cylindrical sleeve 110. ing. A thrust flange 119 is provided at the end of the rotating shaft 109 opposite to the fixed end fixed to the rotor hub 104. The outer diameter of the thrust flange 119 is larger than the inner diameter of the sleeve 110, and the thrust flange 119 also acts as a retainer, so that the relative movement in the axial direction between the rotor hub 104 and the sleeve 110 is prevented. Limited.

(2-5) Spindle motor dynamic pressure bearing unit The outer peripheral surface of the rotating shaft 109 fixed to the rotor hub 104 and the inner peripheral surface of the cylindrical sleeve 110 or both of them are herringbone-shaped shallow. A groove (not shown) is formed, and a lubricating fluid is held in a radial gap between the outer peripheral surface of the rotating shaft 109 and the inner peripheral surface of the sleeve 110. As a result, the pressure of the lubricating fluid is increased when the rotating shaft 109 and the sleeve 110 are rotated, and a radial dynamic pressure bearing 108a that generates a load supporting pressure is formed. A thrust flange 119 provided at the open end of the rotating shaft 109 is accommodated in a radial recess of the sleeve 110, and the lower end of the sleeve is sealed with a bearing lid 121. The upper surface of the thrust flange 119 provided at the end of the rotating shaft 109 faces the lower flat surface of the sleeve 110, and the lower surface faces the upper flat surface of the bearing lid 121. Further, the thrust flange 119 is provided with a spiral shallow groove (not shown) on one or both of its upper surface and lower surface, and the radial recess of the sleeve 110 and the upper surface of the bearing lid 121 and the outer surface of the thrust flange 119 A lubricating fluid is held in the gap. As a result, a thrust dynamic pressure bearing 108b that generates load support pressure in the axial direction when the rotation shaft 109 and the thrust flange 119 rotate relative to the sleeve 110 and the bearing lid 121 is formed. The lubricating fluid is held in a bearing gap that constitutes the radial dynamic pressure bearing 108a and the thrust dynamic pressure bearing 108b. The inner peripheral surface in the vicinity of the opening end of the sleeve 110 is opposed to the outer peripheral surface of the rotating shaft 109, and has a tapered portion 108c in which the gap increases toward the opening end portion of the sleeve 110. An interface 108d is formed with the outside air.

(2-6) Base plate The base plate 103 that forms the base of the spindle motor 102 and forms a part of the casing of the recording disk drive 101 (not shown) has the same shape and configuration as the base plate 3 of the first embodiment. The material and the characteristics in processing are also the same. Similar to the base plate 3 of the first embodiment, the base plate 103 has a hole 113 for fitting the bush 105 therein. In addition, the hole 113 is formed with a hole diameter-enlarging portion 123 whose diameter is increased on the outer peripheral surface of the upper end portion of the hole 113 so that the position in the axial direction can be accurately adjusted in accordance with the shape of the outer peripheral surface of the bush 105. Has been. Since the shapes of the hole 113 and the hole enlarged portion 123 are the same as the shape of the hole 13 and the hole enlarged portion provided in the base plate 3 of the first embodiment, the dynamic pressure bearings having different shapes can be obtained only by changing the shape of the bush 105. The unit can be installed.

(2-7) Spindle Motor Stator and Rotor Magnet The stator 106 includes a 109-slot stator core and a three-phase coil wound around each tooth of the stator core. A sensorless system is used in which a two-phase coil is energized, an induced electromotive force generated in the remaining one-phase coil is converted into a digital signal, and a coil current of each phase is switched. The rotor hub 104 of the spindle motor 102 is rotated by a rotational force due to electromagnetic interaction between the rotor magnet 107 fixed to the rotor hub 104 and the stator 106 whose coil current is controlled opposite to the rotor magnet 107.

(2-8) Bush of spindle motor A substantially cylindrical bush 105 is interposed between the base plate 103 and the hydrodynamic bearing unit 108. The bush 105 includes a short cylindrical portion 105a having a small outer diameter and constituting a lower portion, and a thick portion 105b having a large outer diameter and constituting an upper portion. The short cylindrical portion 105 a is fitted in the hole 113 of the base plate 103, and a part of the thick portion 105 b is fitted in a hole enlarged portion 123 provided in the hole 113 of the base plate 103. The bush is fitted with the outer peripheral surface of a sleeve 110 constituting the hydrodynamic bearing unit 108, and the stator 106 is fitted over the thick portion 105 b of the bush 105.

  This bush 105 has vibration damping properties, and a material having vibration damping properties is used so that the internal loss of vibration energy is large and vibrations from the stator 106 and the dynamic pressure bearing unit 108 are not transmitted to the base plate 103. Yes. As the material having vibration damping properties, a synthetic resin having sufficient work accuracy and mechanical strength is used so that the hydrodynamic bearing unit 108 can be attached to the base plate 103 with high accuracy.

  Note that the member forming the bush 105 may be a metal instead of a resin as long as the member has vibration damping properties. For example, a metal containing Mg is excellent in vibration damping properties, and Mg-Zr is particularly suitable for forming a bush having vibration damping properties. In addition, sintered metal having innumerable voids inside has a large internal loss of energy due to its properties, and has vibration damping properties. If sufficient mechanical strength and work accuracy can be obtained, rubber may be used, and the rubber in this case may be natural rubber or synthetic rubber.

It is sectional drawing of the recording disk drive device described in Example 1 of this invention. It is sectional drawing of the spindle motor used for the recording disk drive device which has a structure as described in Example 1 of this invention. It is sectional drawing of the spindle motor mounted in the recording disk drive device which has a structure as described in Example 2 of this invention.

Explanation of symbols

A Arm B Screw C Clamp D Recording disk H Head P Actuator S Spacer 1, 101 Recording disk drive 2, 102 Spindle motor 3, 103 Base plate 13, 113 Hole 23, 123 Hole enlarged portion 4, 104 Rotor hub 14, 114 Rotor hub ２４ part 24 Cylindrical peripheral wall part 5, 105 Bush 5a, 105a Short cylindrical part 5b, 105b Thick part 6, 106 Stator 7, 107 Rotor magnet 8, 108 Dynamic pressure bearing unit 8a, 108a Radial dynamic pressure bearing 8b, 108b Thrust movement Pressure bearings 8c, 108c Tapered portions 8d, 108d Interfaces 9, 109 Rotating shaft 119 Thrust flange 10, 110 Sleeve 11 Bearing housing 121 Bearing lid

Claims (6)

A spindle motor that is mounted on a recording disk drive and rotates the recording disk,
A base plate constituting at least a part of a housing of the recording disk drive device and forming a base of the spindle motor;
A substantially cylindrical bush fixed to the base plate;
A stator that is externally fitted to the bush and generates a magnetic field when a current flows;
A hydrodynamic bearing unit fitted in the inner periphery of the bush;
A rotating member rotatably supported with respect to the base plate via the dynamic pressure bearing unit;
A spindle motor comprising a rotor magnet fixed to the rotating member so as to face the stator.   The spindle motor according to claim 1, wherein a hole is provided in the base plate, and a part of an outer peripheral surface of the bush is fitted and fixed in the hole.   The hydrodynamic bearing unit has a rotating shaft provided at the rotation center of the rotating member and a cylindrical sleeve that rotatably supports the rotating shaft, and an outer peripheral surface of the rotating shaft and an inner peripheral surface of the sleeve The spindle motor according to claim 1, wherein a radial dynamic pressure bearing portion that supports a load in a radial direction is provided between the spindle motor and the spindle motor.   4. The spindle motor according to claim 1, wherein the material forming the bush is a material having vibration damping properties.   The spindle motor according to claim 1, wherein the material forming the bush is a high-strength material. A spindle motor according to claim 1;
A recording disk placed on the rotating member;
A recording disk drive comprising: information access means for reading and / or writing information on the recording disk.

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